The document discusses the greenhouse effect and global warming. It explains how greenhouse gases like carbon dioxide and methane absorb infrared radiation, trapping heat in the lower atmosphere and maintaining the Earth's temperature. However, increased emissions of these gases are enhancing the greenhouse effect and causing global warming. If emissions are not reduced, climate change effects like rising sea levels and temperatures could severely impact ecosystems and human life. International agreements have aimed to limit carbon dioxide emissions but reducing them further is still needed to curb global warming.

2.  Energy entering the Earth’s atmosphere
coming from the Sun is in the ultraviolet, visible
and infrared regions of the electromagnetic
spectrum.
 As a result of the Earth’s temperature being
lower than that of the Sun, the radiation being
re-emitted from the Earth has a lower amount
of energy and is in the infrared region of the
spectrum.
 Water vapour, carbon dioxide and methane
molecules in the atmosphere absorb some of
this radiation. These are some of the
‘greenhouse gases’.

3.  Greenhouse gases are gases which allow
most of the Sun’s ultraviolet and visible
radiation to enter but prevent some of the
Earth’s infrared radiation from leaving.
 The O-H bonds in the water, the C=O bonds
in the carbon dioxide and the C-H bonds in
the methane all vibrate at different
frequencies in the infrared range, and this is
why they absorb the infrared radiation.
 After absorbing the energy from the
infrared radiation, the bonds then re-emit it.
This maintains the Earth’s average surface
temperature, and without it the surface
temperature of the Earth would be
between -20 and -40 degrees Celsius.
 This is called the greenhouse effect.

4.  The greenhouse effect forms a steady system of
equilibrium, where the rate at which energy is being
absorbed by the Earth is equal to the rate at which
energy is being radiated back into space.
 The increase in emissions of greenhouse gases to the
atmosphere is disrupting the balance of the
greenhouse effect.
 Increased levels of carbon dioxide and other
greenhouse gases in the atmosphere, due to various
reasons such as deforestation and the burning of
fossil fuels, have led to more infrared radiation being
absorbed and re-emitted back to Earth than the
amount of energy being radiated back into space,
increasing the temperature of the Earth.
 This is called Global Warming.

5.  The extent to which molecules absorb infrared
radiation is dependant on the way their bonds
vibrate. The more modes of bond vibration
possible, the higher the absorption of infrared
radiation.
 Due to the asymmetric vibrations that affect
the dipole moment of the molecule, molecules
which have 3 or more atoms absorb strongly in
the infrared region.
 Other than carbon dioxide (CO2), water (H2O)
and methane (CH4), there are three other main
greenhouse gases: dinitrogen oxide (N2O),
CFCs, and tropospheric ozone (O3).

6.  The actual greenhouse effect of a given gas
depends on both its atmospheric
concentration AND its ability to absorb infrared
radiation (its ‘greenhouse factor’).
 The greenhouse factor is the extent to which
an atmospheric gas absorbs infrared radiation
relative to the same amount of carbon dioxide.
Carbon dioxide has a value of 1.
 The table on the next slide shows the
contribution of five of the greenhouse gases
that we have mentioned (water is not
included) to the greenhouse effect. It
demonstrates how the greenhouse effect
depends on both atmospheric concentration
of the gases AND greenhouse factor.

7. Gas Greenhouse Concentration in Overall
factor troposphere/pp contribution/%
mv
Carbon dioxide 1 358 60
CO2
Methane 30 1.7 15-20
CH4
Dinitrogen oxide 150 0.3
N2O
Ozone 2000 0.1 (varies) 20-25
O3
CFCs 10000-25000 0.004

8.  The build-up of greenhouse gases in the atmosphere
will lead to an increase in the Earth’s surface
temperature (global warming).
 In 2000 the Earth’s average temperature was 1°C
warmer than the value in 1850.
 Between 1970 and 2000 the rise was 0.4°C.
 The average yearly rise in temperature between 1850
and 1970 was 0.005°C, and between 1970 and 2000 it
was 0.013°C, more than two times the previous value.
 These statistics indicate the rate of acceleration of
global warming. Computer predictions suggest that
the temperature is rising a lot faster than previously
predicted.

9.  The accelerated rise in temperature would be so fast that
natural systems would not be able to adapt and world
food productions would be seriously affected.
 Originally it had been believed that the greater amount of
CO2 in the atmosphere would increase forest growth due
to more photosynthesis, and that this would remove some
carbon dioxide from the atmosphere.
 More recent predictions however provide evidence that
the increased temperatures will increase respiration within
the forests and that this will cause die-back of healthy
plants.
 The model of higher temperatures causing die-back
predicts that the majority of the Amazon rainforest will
disappear due to die-back. As a result of this the carbon in
the wood of the trees would be released as carbon
dioxide, increasing the amount of CO2 in the atmosphere.
Due to the lack of trees, there will also less carbon dioxide
being absorbed for photosynthesis.

10.  The higher temperatures would also increase
microbial activity, and the hotter soil would
cause more releasing of carbon dioxide from
microbes.
 Extreme weather events are also already
occurring more often due to global warming.
 In 1989, it was predicted that the greenhouse
effect would cause a rise in the Earth’s
average temperature of between 1.5 and
2.5°C by 2100, however more recent
predictions suggest that this rise may reach 8°C
above the 1850 level by 2100 for land masses.
 The cuts to CO2 emissions proposed at the
Climate Change Convention will not stop the
predicted changes.

11.  It is now predicted that the level of carbon
dioxide in the atmosphere in 2100 will be
three times the current level, taking into
account die-back of rainforests and
increased soil microbial activity, and
assuming that there is no reduction in CO2
emissions.
 These predictions indicate how necessary it
is to tackle global warming urgently. If no
changes are made, the effects of global
warming will badly affect most areas of life,
including agriculture, sea levels,
ecosystems, water resources, human health
and the weather.

12.  The statistics shown on the last few slides
have been passed on to the government
by chemists, as proof of the devastating
effects of climate change and as
persuasive material to convince the
government to help to fight against global
warming.
 There are a few potential solutions which
have to environmental problems which
have been thought of which could reduce
the amount of carbon dioxide being
released into the atmosphere. These are
discussed on the next slide.

13. 1. Using sources of energy which avoid the burning of fossil fuels.
For example renewable sources such as solar, wind, wave,
tidal and geothermal energy. There is also the possibility of
more nuclear power stations . These would reduce CO2
emissions but there are many other environmental concerns
associated with them.
2. Conserving energy to reduce the burning of fossil fuels.
3. CCS-carbon capture and storage. This method involves
capturing carbon dioxide released from power stations or
industrial processes, and potentially storing it underground or
into the deep oceans. Storing the CO2 in the deep oceans is
seen as ideal because it can take centuries for the deep
waters to reach the surface. However, there are fears that this
will eventually acidify the oceans, causing damage to the
ecosystem. Pumping the CO2 underground would help us to
get the few remaining supplies of oil and gas to the surface,
and the CO2 can react with metal oxides in the rock to form
solid carbonates or can dissolve in the salty water trapped
underground. Many locations in the UK are suitable for this
type of CCS.

14.  Some international treaties have been held targeting
the reduction of carbon dioxide emissions in order to
combat climate change.
 In December 2006, the Kyoto Protocol was signed by
169 countries, stating that they would reduce CO2
emissions.
 This was a big step, the USA and Australia, some of
the largest producers of carbon dioxide, refused to
sign it.
 Also countries which were seen as still developing
industrially, such as China and India, did not have to
reduce their emissions.
 Chemists, using techniques such as infrared
spectroscopy, with infrared spectrometers based on
satellites in the sky, have a significant role in
monitoring agreements such as the Kyoto Protocol,
as they can measure the levels of carbon dioxide
emissions coming from different areas of the planet.